367 research outputs found
Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies
We present carbon abundances of red giants in Milky Way globular clusters and
dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon
abundances for 154 giants in the clusters NGC 2419, M68, and M15 and 398 giants
in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the
number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the
clusters decreases with increasing luminosity above log(L/L_sun) ~= 1.6, which
can be explained by deep mixing in evolved giants. The same decrease is
observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform.
Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize
that [C/Fe] (corrected to the initial carbon abundance) declines with
increasing [Fe/H] due to the metallicity dependence of the carbon yield of
asymptotic giant branch stars and due to the increasing importance of Type Ia
supernovae at higher metallicities. We also identified 11 very carbon-rich
giants (8 previously known) in three dSphs. However, our selection biases
preclude a detailed comparison to the carbon-enhanced fraction of the Milky Way
stellar halo. Nonetheless, the stars with [C/Fe] < +1 in dSphs follow a
different [C/Fe] track with [Fe/H] than the halo stars. Specifically, [C/Fe] in
dSphs begins to decline at lower [Fe/H] than in the halo. The difference in the
metallicity of the [C/Fe] "knee" adds to the evidence from [alpha/Fe]
distributions that the progenitors of the halo had a shorter timescale for
chemical enrichment than the surviving dSphs.Comment: accepted to ApJ; 20 pages, 11 figures, 2 machine-readable table
Ecosystem service multifunctionality and trade-offs in English Green Belt peri-urban planning
Green Belt policies govern peri-urban landscapes globally by restricting built development. Yet, they often have little consideration for the land within them. This is especially the case in England where ecosystem services are poorly accounted for in Green Belt policy, whilst also being viewed as a development obstacle, with few environmental and social benefits; a situation mirrored in peri-urban landscapes globally. Moreover, there is a significant research gap into Green Belts through the socio-ecological lenses of ecosystem services and multifunctionality, which allows populist discourses to go unchallenged. Using modelling and participatory mapping data this paper addresses this gap by quantifying the ecosystem service supply, trade-offs and multifunctionality of the North-East Green Belt, and the wider planning and policy implications. The results show that contrary to claims, Green Belts in England can and do provide multiple benefits to people when studied through these lenses. However, levels of individual ecosystem services and overall multifunctionality differ spatially within Green Belts resulting in opportunity areas as well as potential losses of ecosystem services from development. Areas of deciduous and coniferous woodland as well as key âgreen wedgesâ close to urban populations were found to be multifunctionality âhots-spotsâ, whereas arable and improved grassland provide notable âcold-spotsâ. Trade-offs were mostly from provisioning services. We argue that Green Belt policies explicitly and holistically accounting for ecosystem services could catalyse a multifunctional opportunity space for climate, nature and people in peri-urban landscapes. Additionally, our study demonstrates the conceptual merits of ecosystem service multifunctionality for planning.This work was supported by the Natural Environment Research Council funded ONE Planet Doctoral Training Partnership [NE/ S007512/1]
Transcending Scale Dependence in Identifying Habitat with Resource Selection Functions
Multi-scale resource selection modeling is used to identify factors that limit species distributions across scales of space and time. This multi-scale nature of habitat suitability complicates the translation of inferences to single, spatial depictions of habitat required for conservation of species. We estimated resource selection functions (RSFs) across three scales for a threatened ungulate, woodland caribou (Rangifer tarandus caribou), with two objectives: (1) to infer the relative effects of two forms of anthropogenic disturbance (forestry and linear features) on woodland caribou distributions at multiple scales and (2) to estimate scale-integrated resource selection functions (SRSFs) that synthesize results across scales for management-oriented habitat suitability mapping. We found a previously undocumented scale-specific switch in woodland caribou response to two forms of anthropogenic disturbance. Caribou avoided forestry cut-blocks at broad scales according to first-and second-order RSFs and avoided linear features at fine scales according to third-order RSFs, corroborating predictions developed according to predator-mediated effects of each disturbance type. Additionally, a single SRSF validated as well as each of three single-scale RSFs when estimating habitat suitability across three different spatial scales of prediction. We demonstrate that a single SRSF can be applied to predict relative habitat suitability at both local and landscape scales in support of critical habitat identification and species recovery
The Binary Fraction of Stars in Dwarf Galaxies: The Cases of Draco and Ursa Minor
Measuring the frequency of binary stars in dwarf spheroidal galaxies (dSphs) requires data taken over long time intervals. We combine radial velocity measurements from five literature sources taken over the course of ~30 years to yield the largest multi-epoch kinematic sample for stars in the dSphs Draco and Ursa Minor. With this data set, we are able to implement an improved version of the Bayesian technique described in Spencer et al. to evaluate the binary fraction of red giant stars in these dwarf galaxies. Assuming Duquennoy & Mayor period and mass ratio distributions, the binary fractions in Draco and Ursa Minor are 0.50_(-0.06)^(+0.04) and 0.78_(-0.08)^(+0.09), respectively. We find that a normal mass ratio distribution is preferred over a flat distribution, and that log-normal period distributions centered on long periods ”_(log P > 3.5) are preferred over distributions centered on short ones. We reanalyzed the binary fractions in Leo II, Carina, Fornax, Sculptor, and Sextans, and find that there is <1% chance that binary fraction is a constant quantity across all seven dwarfs, unless the period distribution varies greatly. This indicates that the binary populations in Milky Way dSphs are not identical in regard to their binary fractions, period distributions, or both. We consider many different properties of the dwarfs (e.g., mass, radius, luminosity, etc.) and find that binary fraction might be larger in dwarfs that formed their stars quickly and/or have high velocity dispersions
Stellar kinematics of dwarf galaxies from multi-epoch spectroscopy: application to Triangulum II
We present new MMT/Hectochelle spectroscopic measurements for 257 stars
observed along the line of sight to the ultra-faint dwarf galaxy Triangulum II.
Combining with results from previous Keck/DEIMOS spectroscopy, we obtain a
sample that includes 16 likely members of Triangulum II, with up to 10
independent redshift measurements per star. To this multi-epoch kinematic data
set we apply methodology that we develop in order to infer binary orbital
parameters from sparsely sampled radial velocity curves with as few as two
epochs. For a previously-identified (spatially unresolved) binary system in
Tri~II, we infer an orbital solution with period , semi-major axis , and a systemic velocity that we then use in the analysis of Tri~II's
internal kinematics. Despite this improvement in the modeling of binary star
systems, the current data remain insufficient to resolve the velocity
dispersion of Triangulum II. We instead find a 95% confidence upper limit of
Tools for delivering entomopathogenic fungi to malaria mosquitoes: effects of delivery surfaces on fungal efficacy and persistence.
BACKGROUND\ud
\ud
Entomopathogenic fungi infection on malaria vectors increases daily mortality rates and thus represents a control measure that could be used in integrated programmes alongside insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). Before entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed.\ud
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METHODS\ud
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The efficacy of Metarhizium anisopliae ICIPE-30 and Beauveria bassiana I93-825 (IMI 391510) (2 Ă 10(10) conidia m(-2)) applied on mud panels (simulating walls of traditional Tanzanian houses), black cotton cloth and polyester netting was evaluated against adult Anopheles gambiae sensu stricto. Mosquitoes were exposed to the treated surfaces 2, 14 and 28 d after conidia were applied. Survival of mosquitoes was monitored daily.\ud
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RESULTS\ud
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All fungal treatments caused a significantly increased mortality in the exposed mosquitoes, descending with time since fungal application. Mosquitoes exposed to M. anisopliae conidia on mud panels had a greater daily risk of dying compared to those exposed to conidia on either netting or cotton cloth (p < 0.001). Mosquitoes exposed to B. bassiana conidia on mud panels or cotton cloth had similar daily risk of death (p = 0.14), and a higher risk than those exposed to treated polyester netting (p < 0.001). Residual activity of fungi declined over time; however, conidia remained pathogenic at 28 d post application, and were able to infect and kill 73 - 82% of mosquitoes within 14 d.\ud
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CONCLUSION\ud
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Both fungal isolates reduced mosquito survival on immediate exposure and up to 28 d after application. Conidia were more effective when applied on mud panels and cotton cloth compared with polyester netting. Cotton cloth and mud, therefore, represent potential substrates for delivering fungi to mosquitoes in the field
Stellar Velocities in the Carina, Fornax, Sculptor and Sextans dSph Galaxies: Data from the Magellan/MMFS Survey
We present spectroscopic data for individual stars observed from 2004 March
through 2008 August as part of our Michigan/MIKE Fiber System (MMFS) survey of
four dwarf spheroidal (dSph) galaxies: Carina, Fornax, Sculptor and Sextans.
Using MMFS at the Magellan/Clay Telescope at Las Campanas Observatory, we have
acquired 8855 spectra from 7103 red giant candidates in these Galactic
satellites. We list measurements of each star's line-of-sight velocity (median
error +/- 2.1 km/s) and spectral line indices for iron and magnesium absorption
features. We use globular cluster spectra to calibrate the indices onto
standard [Fe/H] metallicity scales, but comparison of the resulting
metallicities with published values suggests that the MMFS indices are best
used as indicators of relative, not absolute metallicity. The empirical
distributions of velocity and spectral indices also allow us to quantify the
amount of contamination by foreground stars. In a companion paper we develop an
algorithm that evaluates the membership probability for each star, showing that
the present MMFS sample contains more than 5000 dSph members, including 774
Carina members, 2483 Fornax members, 1365 Sculptor members, and 441 Sextans
members.Comment: Accepted for publication in The Astronomical Journal. Full data
tables will be included in the electronic article, and are available at
http://www.ast.cam.ac.uk/~walker/mmfsdata.htm
Evolution of opinions on social networks in the presence of competing committed groups
Public opinion is often affected by the presence of committed groups of
individuals dedicated to competing points of view. Using a model of pairwise
social influence, we study how the presence of such groups within social
networks affects the outcome and the speed of evolution of the overall opinion
on the network. Earlier work indicated that a single committed group within a
dense social network can cause the entire network to quickly adopt the group's
opinion (in times scaling logarithmically with the network size), so long as
the committed group constitutes more than about 10% of the population (with the
findings being qualitatively similar for sparse networks as well). Here we
study the more general case of opinion evolution when two groups committed to
distinct, competing opinions and , and constituting fractions and
of the total population respectively, are present in the network. We show
for stylized social networks (including Erd\H{o}s-R\'enyi random graphs and
Barab\'asi-Albert scale-free networks) that the phase diagram of this system in
parameter space consists of two regions, one where two stable
steady-states coexist, and the remaining where only a single stable
steady-state exists. These two regions are separated by two fold-bifurcation
(spinodal) lines which meet tangentially and terminate at a cusp (critical
point). We provide further insights to the phase diagram and to the nature of
the underlying phase transitions by investigating the model on infinite
(mean-field limit), finite complete graphs and finite sparse networks. For the
latter case, we also derive the scaling exponent associated with the
exponential growth of switching times as a function of the distance from the
critical point.Comment: 23 pages: 15 pages + 7 figures (main text), 8 pages + 1 figure + 1
table (supplementary info
Crater 2::An Extremely Cold Dark Matter Halo
<p>supplementary data products, including all sky-subtracted spectra from individual targets, as well as random draws from posterior PDFs for model parameters (see enclosed README file)</p>
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